1. Field of the Invention
The present invention relates to sealed relays, and particularly to high voltage operation sealed relays in low permeability plastic housings.
2. Description of the Related Art
Hermetically sealed electromagnetic relays are used for switching of high electrical currents and/or high voltages, and typically have fixed and movable internal contacts, and an internal actuating mechanism supported within a hermetically sealed housing. In one type of relay air is removed from the relay housing to create a vacuum that suppresses arc formation, provides long operating life and allows for low resistance operation of the relay. In another type of relay, the evacuated chamber can be backfilled under pressure with an insulating gas, which allows the relay to operate with good arc-suppressing properties.
One type of conventional relay has moving components housed within a ceramic housing. These types of relays can operate effectively with a vacuum formed in the housing or with the housing having internal pressure from an injected gas. This allows the relays to operate with high voltage and/or low resistance characteristics and ceramic housings also allow the relays to operate at high temperature. Ceramic housings, however, are typically expensive, difficult to manufacture and offer limited flexibility in the shape and variety of use.
U.S. Pat. No. 4,039,984 to DeLucia et al. generally discloses a high-voltage magnetic relay enclosed within a housing of insulating material which contains a gas, such as sulfur hexafluoride. The terminals within the housing extend through its wall and are secured to and sealed to the housing to prevent gas from leaking from the housing. Leads are connected to the terminals externally of the housing, with insulating material surrounding the leads and being secured by the terminals to the housing. An operating mechanism within the housing shifts a pivoted arm electrically connected to one of the terminals within the housing into and from contact with another of the terminals within the housing. The housing is made from a material that has high impact strength and high heat resistance such as a polyamide or polycarbonate resins.
U.S. Pat. No. 4,168,480 to DeLucia discloses a high voltage magnetic relay that is enclosed by an insulating housing containing a gas, such as sulfur hexafluoride, under pressure. The switch terminals removably extend through a wall of the housing and are sealed. The magnet relay structure is removably connected to the housing by a sealed joint. A fill valve extends through a wall of the housing and is sealed to the housing. The armature shifts a pivotal arm in the housing between open and closed contact positions. The housing is formed of a polyamide material that is resistant to deterioration by fluorine gas, the material being poly hexamethylene terephthalic amide.
U.S. Pat. No. 5,554,963 to Johler et al. discloses a relay that includes a plastic enclosure, contacts disposed in the plastic enclosure for selectively operating to make and/or break at least one electrical connection, a gas filling containing at least one electronegative gas, and a sealed plastic encapsulation for preventing the at least one electronegative gas from diffusing away. The electronegative gases are not utilized at high pressure, but under atmospheric pressure or slightly higher pressure. Since normal pressure is used, a hermetically sealed encapsulation can be dispensed with and the enclosure can be made of low-cost plastics without connection to the outside air.
U.S. Pat. No. 6,265,955 to Molyneux et al. generally discloses a relay having a primary external sidewall formed by a plastic potting cup with a sealed chamber arranged within the cup and having the relay's moving components. The cup is enclosed at the bottom by a base, with the base and cup serving as a mold to hold epoxy material poured into the cup and cured to provide a hermetic seal. Insulated electrical leads extend through the epoxy material from the sealed chamber for connection of fixed and movable contacts to external circuitry. The base can have a threaded portion that extends from the underside of cup. The potting cup is preferably formed of Nylon 6/6.